New activity/unrest was observed at 4 volcanoes between May 4 and 10, 2016. During the same period, ongoing activity was reported for 19 volcanoes.
New activity/unrest: Bristol Island, South Sandwich Islands (UK) | Nevados de Chillán, Chile | Ruapehu, North Island (New Zealand) | White Island, North Island (New Zealand).
Ongoing activity: Aira, Kyushu (Japan) | Alaid, Kuril Islands (Russia) | Bagana, Bougainville (Papua New Guinea) | Chirpoi, Kuril Islands (Russia) | Cleveland, Chuginadak Island (USA) | Colima, Mexico, Dukono | Halmahera (Indonesia) | Fuego, Guatemala | Kerinci, Indonesia | Kilauea, Hawaiian Islands (USA) | Klyuchevskoy, Central Kamchatka (Russia) | Langila, New Britian (Papua New Guinea) | Masaya, Nicaragua | Nevado del Ruiz, Colombia | Sangay, Ecuador | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Suwanosejima, Ryukyu Islands (Japan) | Turrialba, Costa Rica.
Bristol Island, South Sandwich Islands (UK)
59.063°S, 26.587°W, Elevation 1100 m
Based on analysis of satellite images, an eruption at Bristol Island likely began on 24 April, the first eruption since 1956. Landsat images detected a plume and a thermal anomaly in the main crater at the top of Mt. Sourabaya. By 1 May the anomaly was elongated to the W, suggesting that lava had breached the crater rim.
Geological summary: The 9 x 10 km Bristol Island near the southern end of the South Sandwich arc lies across Fortser's Passage from the Southern Thule Islands and forms one of the largest islands of the chain. Largely glacier-covered, it contains a horseshoe-shaped ridge at the interior extending northward from the highest peak, 1100-m-high Mount Darnley. A steep-sided flank cone or lava dome, Havfruen Peak, is located on the east side, and a young crater and fissure are on the west flank. Three large sea stacks lying off Turmoil Point at the western tip of the island may be remnants of an older now-eroded volcanic center. Both summit and flank vents have been active during historical time. The latest eruption, during 1956, originated from the west-flank crater, and deposited cinder over the icecap. The extensive icecap and the difficulty of landing make it the least explored of the South Sandwich Islands.
Nevados de Chillán, Chile
36.863°S, 71.377°W, Elevation 3212 m
Servicio Nacional de Geología and Minería (SERNAGEOMIN) Observatorio Volcanológico de Los Andes del Sur (OVDAS) reported that the seismic stations monitoring Nevados de Chillán's Volcán Arrau dome complex recorded an explosion at 1303 on 9 May; an associated plume rose 1.7 km above the crater rim. The Alert Level remained at Yellow, the middle level on a three-color scale, and the public was reminded not to approach the craters within a 2-km radius.
Geological summary: The compound volcano of Nevados de Chillán is one of the most active of the Central Andes of Chile. Three late-Pleistocene to Holocene stratovolcanoes were constructed along a NNW-SSE line within three nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile. The largest stratovolcano, dominantly andesitic, 3212-m-high Cerro Blanco (Volcán Nevado), is located at the NW end of the group, and 3089-m-high Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The new Volcán Nuevo lava-dome complex formed between 1906 and 1945 between the two volcanoes and grew to exceed Volcán Viejo in altitude. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986, eventually exceeding its height by 20 m.
Ruapehu, North Island (New Zealand)
39.28°S, 175.57°E, Elevation 2797 m
GeoNet reported that a volcanic earthquake swarm beneath Ruapehu's summit Crater Lake was detected during 25-26 April. This type of swarm has been uncommon at the volcano in recent years, when volcanic tremor has dominated the seismicity. In addition, the crater lake water temperature had been rising since late 2015, from 25 degrees Celsius to 40 degrees in the last half of April. Similar temperature increases were detected in March 2011, April 2014, and February 2015.
In a 3 May notice GeoNet stated that the size and number of events in the swarm had decreased; a period of moderate volcanic tremor began at 1310 on 2 May and lasted about an hour. The lake temperature had peaked at 42 degrees, equal to the highest recorded temperature since 2011. At around 1400 on 7 May tourists on an overflight of the area observed vigorous steaming at the lake surface and upwelling bubbles. The lake temperature rose further, to 44 degrees, establishing a new high since temperatures started to be recorded in 2000. The earthquake swarm had stopped, though the seismic network continued to record volcanic tremor. On 11 May GeoNet stated that recent visits to the lake confirmed increased gas emissions from the crater lake. The lake temperature increased to 46 degrees and moderate levels of volcanic tremor continued. The Volcanic Alert Level was raised to 2 (moderate to heightened unrest) and the Aviation Colour Code was raised to Yellow.
Geological summary: Ruapehu, one of New Zealand's most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes dating back to about 200,000 years ago. The 110 cu km dominantly andesitic volcanic massif is elongated in a NNE-SSW direction and surrounded by another 100 cu km ring plain of volcaniclastic debris, including the Murimoto debris-avalanche deposit on the NW flank. A series of subplinian eruptions took place between about 22,600 and 10,000 years ago, but pyroclastic flows have been infrequent. A single historically active vent, Crater Lake, is located in the broad summit region, but at least five other vents on the summit and flank have been active during the Holocene. Frequent mild-to-moderate explosive eruptions have occurred in historical time from the Crater Lake vent, and tephra characteristics suggest that the crater lake may have formed as early as 3000 years ago. Lahars produced by phreatic eruptions from the summit crater lake are a hazard to a ski area on the upper flanks and to lower river valleys.
White Island, North Island (New Zealand)
37.52°S, 177.18°E, Elevation 321 m
GeoNet reported that activity at White Island decreased following the eruption on 27 April; both volcanic gas output and seismic activity had decreased, and visual observations on 6 May confirmed that no further activity had occurred. The Volcanic Alert Level was lowered to 1 and the Aviation Colour Code remained at Yellow.
Geological summary: Uninhabited 2 x 2.4 km White Island, one of New Zealand's most active volcanoes, is the emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The 321-m-high island consists of two overlapping andesitic-to-dacitic stratovolcanoes; the summit crater appears to be breached to the SE because the shoreline corresponds to the level of several notches in the SE crater wall. Volckner Rocks, four sea stacks that are remnants of a lava dome, lie 5 km NNE of White Island. Intermittent moderate phreatomagmatic and strombolian eruptions have occurred at White Island throughout the short historical period beginning in 1826, but its activity also forms a prominent part of Maori legends. Formation of many new vents during the 19th and 20th centuries has produced rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project.
Aira, Kyushu (Japan)
31.593°N, 130.657°E, Elevation 1117 m
JMA reported that on 8 May explosions from Showa Crater (at Aira Caldera’s Sakurajima volcano) generated an ash plume that rose 3.3 km above the crater rim and ejected tephra as far as 1.3 km from the crater. The Alert Level remained at 3 (on a 5-level scale).
Geological summary: The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.
Alaid, Kuril Islands (Russia)
50.861°N, 155.565°E, Elevation 2285 m
KVERT reported that moderate activity at Alaid continued during 29 April-6 May. Satellite images showed an intense daily thermal anomaly over the volcano. TheAviation Color Code remained at Orange (the second highest level on a four-color scale).
Geological summary: The highest and northernmost volcano of the Kuril Islands, 2285-m-high Alaid is a symmetrical stratovolcano when viewed from the north, but has a 1.5-km-wide summit crater that is breached widely to the south. Alaid is the northernmost of a chain of volcanoes constructed west of the main Kuril archipelago and rises 3000 m from the floor of the Sea of Okhotsk. Numerous pyroclastic cones dot the lower flanks of basaltic to basaltic-andesite Alaid volcano, particularly on the NW and SE sides, including an offshore cone formed during the 1933-34 eruption. Strong explosive eruptions have occurred from the summit crater beginning in the 18th century. Reports of eruptions in 1770, 1789, 1821, 1829, 1843, 1848, and 1858 were considered incorrect by Gorshkov (1970). Explosive eruptions in 1790 and 1981 were among the largest in the Kuril Islands during historical time.
Bagana, Bougainville (Papua New Guinea)
6.137°S, 155.196°E, Elevation 1855 m
Based on analyses of satellite imagery and model data, the Darwin VAAC reported that during 4-9 May ash plumes from Bagana rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted almost 140 km SW and W.
Geological summary: Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical, roughly 1850-m-high cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50-m-thick with prominent levees that descend the volcano's flanks on all sides. Satellite thermal measurements indicate a continuous eruption from before February 2000 through at least late August 2014.
Chirpoi, Kuril Islands (Russia)
46.525°N, 150.875°E, Elevation 742 m
SVERT reported that a thermal anomaly over Snow, a volcano of Chirpoi, was detected in satellite images on 2 and 5 May. The Aviation Color Code remained at Yellow.
Geological summary: Chirpoi, a small island lying between the larger islands of Simushir and Urup, contains a half dozen volcanic edifices constructed within an 8-9 km wide, partially submerged caldera. The southern rim of the caldera is exposed on nearby Brat Chirpoev Island. The symmetrical Cherny volcano, which forms the 691 m high point of the island, erupted twice during the 18th and 19th centuries. The youngest volcano, Snow, originated between 1770 and 1810. It is composed almost entirely of lava flows, many of which have reached the sea on the southern coast. No historical eruptions are known from 742-m-high Brat Chirpoev, but its youthful morphology suggests recent strombolian activity.
Cleveland, Chuginadak Island (USA)
52.825°N, 169.944°W, Elevation 1730 m
AVO reported that an explosion at Cleveland was detected at 1844 on 5 May by both infrasound (air pressure) sensors and seismic data. AVO raised the Level ofConcern Color Code to Orange and the Volcano Alert Level to Watch. Satellite views the next day were obscured by clouds; no signs of ash was detected above the cloud deck. AVO noted that the event likely modified the new, small lava dome that had been growing in the summit crater since the previous explosion on 16 April. No activity was observed in satellite images nor detected by the seismic and infrasound networks during 6-8 May. A small explosion was detected at 0732 on 10 May by infrasound sensors. A minor amount of ash was possibly generated by the explosion, but nothing was detected in satellite data and AVO received no reports of ash emissions from local observers or passing pilots.
Geological summary: Beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited, dumbbell-shaped Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Cleveland is joined to the rest of Chuginadak Island by a low isthmus. The 1730-m-high Mount Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name for Mount Cleveland, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.
19.514°N, 103.62°W, Elevation 3850 m
Based on information from Colima Towers and the Mexico City MWO, and webcam and satellite views, the Washington VAAC reported that on 4, 6, and 9-10 May ash plumes from Colima rose to altitudes of 5.2-6.1 km (17,000-20,000 ft) a.s.l. and drifted NW, NE, and E.
Geological summary: The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4320 m high point of the complex) on the north and the 3850-m-high historically active Volcán de Colima at the south. A group of cinder cones of late-Pleistocene age is located on the floor of the Colima graben west and east of the Colima complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.
Dukono, Halmahera (Indonesia)
1.693°N, 127.894°E, Elevation 1229 m
Based on analyses of satellite imagery and wind data, and notices from PVMBG, the Darwin VAAC reported that during 4-10 May ash plumes from Dukono rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted over 165 km NW, W, and WSW.
Geological summary: Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time
14.473°N, 90.88°W, Elevation 3763 m
INSIVUMEH reported that during 7-10 May weak-to-moderate explosions at Fuego generated ash plumes that rose 550-750 m above the crater and drifted S, SW, and W.
Geological summary: Volcán Fuego, one of Central America's most active volcanoes, is one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between 3763-m-high Fuego and its twin volcano to the north, Acatenango. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at Acatenango. In contrast to the mostly andesitic Acatenango, eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.
1.697°S, 101.264°E, Elevation 3800 m
Based on reports from PVMBG and satellite data, the Darwin VAAC reported that on 4 May an ash plume from Kerinci rose to an altitude of 4.3 km (14,000 ft)a.s.l. and drifted WSW
Geological summary: The 3800-m-high Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. Kerinci is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. The volcano contains a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit of Kerinci. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. The frequently active Gunung Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.
Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W, Elevation 1222 m
HVO reported that seismicity beneath Kilauea's summit, upper East Rift Zone, and Southwest Rift Zone was at background levels during 4-10 May. The lava lake continued to circulate and eject spatter in the Overlook vent. Webcams recorded outgassing from multiple spatter cones on the Pu'u 'O'o Crater floor. A small lava flow from a NE vent intermittently flowed onto the crater floor during 4-5 and 7 May. The June 27th NE-trending lava flow continued to be active within 5.8 km NE of Pu'u 'O'o Crater.
Geological summary: Kilauea volcano, which overlaps the east flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions of Kilauea are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 sq km, destroying nearly 200 houses and adding new coastline to the island.
Klyuchevskoy, Central Kamchatka (Russia)
56.056°N, 160.642°E, Elevation 4754 m
KVERT reported that a Strombolian eruption at Klyuchevskoy continued during 29 April-6 May. Satellite and video data showed a lava flow effusing on the SE flank, down the Apakhonchich drainage. Satellite images showed an intense thermal anomaly over the volcano, and an ash cloud that drifted 88 km SE on 2 May. The Aviation Color Code was raised to Orange.
Geological summary: Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.
Langila, New Britian (Papua New Guinea)
5.525°S, 148.42°E, Elevation 1330 m
Based on analyses of satellite imagery and RVO ground observations, the Darwin VAAC reported that during 9-10 May ash plumes from Langila rose to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l. and drifted 75 km N, NW, and W.
Geological summary: Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila volcano was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the north and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit of Langila. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.
11.984°N, 86.161°W, Elevation 635 m
INETER reported that between 1700 and 2400 on 3 May volcanic tremor at Masaya increased; RSAM values spiked at 1,000 units and then dropped to 250. Gas emissions at Santiago crater were at low-to-moderate levels, and the lava lake continued to strongly circulate. On 5 May RSAM values fluctuated between 250 and 500 units, which are low-to-moderate values.
Geological summary: Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The twin volcanoes of Nindirí and Masaya, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic plinian tephra erupted from Masaya about 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals cause health hazards and crop damage.
Nevado del Ruiz, Colombia
4.892°N, 75.324°W, Elevation 5279 m
Based on webcam views and information from SGC, the Washington VAAC reported that on 5 May an ash emission from Nevado del Ruiz rose to an altitude of 6.7 km (22,000 ft) a.s.l. and drifted NW.
Geological summary: Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers >200 sq km. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.
2.005°S, 78.341°W, Elevation 5286 m
Based on satellite images, notices from the Guayaquil MWO, and information from IG, the Washington VAAC reported that during 4-7 and 9-10 May ash plumes from Sangay rose to altitudes of 6.1-8.2 km (20,000-27,000 ft) a.s.l. and drifted as far as 55 km NW, W, WSW, and SW. An intermittent thermal anomaly was identified in satellite images during 4-5 and 10 May.
Geological summary: The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes, and its most active. The dominantly andesitic volcano has been in frequent eruption for the past several centuries. The steep-sided, 5230-m-high glacier-covered volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Elevation 3283 m
KVERT reported that during 29 April-6 May lava-dome extrusion onto Sheveluch’s N flank was accompanied by strong fumarolic activity, dome incandescence,ash explosions, and hot avalanches. Satellite images showed an intense daily thermal anomaly over the dome, and ash plumes drifting 36 km SE on 2 May. The Aviation Color Code remained at Orange.
Geological summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 cu km volcano is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.
3.17°N, 98.392°E, Elevation 2460 m
Based on satellite images and information from PVMBG, the Darwin VAAC reported that during 4-5 and 9-10 May ash plumes from Sinabung rose to altitudes of 3.6-4.8 km (12,000-16,000 ft) a.s.l. and drifted W.
Geological summary: Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical, 2460-m-high andesitic-to-dacitic volcano is at the southern end of the four overlapping summit craters. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.
Suwanosejima, Ryukyu Islands (Japan)
29.638°N, 129.714°E, Elevation 796 m
Based on JMA notices, the Tokyo VAAC reported that during 4-5 May explosions at Suwanosejima generated ash plume that rose to altitudes of 1.5-2.1 km (5,000-7,000 ft) a.s.l. and drifted SE.
Geological summary: The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.
Turrialba, Costa Rica
10.025°N, 83.767°W, Elevation 3340 m
OVSICORI-UNA reported that frequent small explosions and sustained tremor with significant and variable amplitude continued to be recorded at Turrialba during 3-5 May. Ash plumes rose 500 m above West Crater and drifted NW and SE, though larger explosions generated ash plumes that rose as high as 1 km. During 6-7 May gas-and-water-vapor plumes rose 1 km. Tremor was characterized as having short duration and a moderate amplitude; for a period between 0530 and 1700 on 7 May tremor amplitude was high but then afterwards it drastically decreased and a significant number of discrete volcanic earthquakes were recorded. Small lahars descended drainages on the upper flanks, mainly in the Río Aquiares drainage. During 0200-0900 on 8 May small, frequent ash emissions, that rose no more than 500 m, were observed coincident with the detection of spasmodic tremor. Gas emissions rose 500 m above the crater at least until noon on 10 May. The amplitude of the volcanic tremor decreased and remained low.
Geological summary: Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive 3340-m-high Turrialba is exceeded in height only by Irazú, covers an area of 500 sq km, and is one of Costa Rica's most voluminous volcanoes. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.
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